Stencil sheet for use in duplicating typewritten or manuscript documents, drawings, and the like



Patented Aug. 18, 1931 UNITED STATES PATENT OFFICE ARMAND DE WAELE, OF OLD SOUTHGATE, LONDON, ENGLAND, ASSIGNOR T D. GESTETNER, LIMITED, 01 LONDON, ENGLAND STENCIL SHEET FOR USE IN DUPLICATING TYPEWBITTEN 0R MANUSCRIPT DOCU- MENTS, DRAWINGS, AND THE LIKE No Drawing. Application filed January 22, 1929, Serial No. 884,870, and in Great Britain February 23, 1928.

ljhis invention relates to stencil sheets for use" 1n duplicating typewritten or manuscript documents, drawings and the like of the kind adapted to be stencilized by pressure applied, 5 for. instance, by means of a style or by type faces, the ink-resisting medium of the stencil consisting of a gelatinizing organic colloid 1n association with a material adapted to temper or modify the character of the colloid in such manner that the structure of the inkresisting medium may be broken down or the medium pushed aside where pressure is applied thereto in the operation of stencil- 1z1ng.

Gelatinizing organic colloids of somewhat widely varying character have been employed in the production of such stencil sheets during a number of years and among other gelatinizing organic colloids proteins, such as gelatine, have been used. At one period in the development of such stencil sheets an aqueous medium was applied to the gelatine immediately before cutting the stencil; at a somewhat later date the inclusion in the ink-resisting medium of hygroscopic materials adapted to retain a suflicient proportion of water therein to temper the gelatine was proposed.

Recently stencil sheets the ink-resisting media of which include proteins or other gelatinizing organic. colloids have been produced which do not need moistening prior to stencilizing and which furthermore do not contain any material proportion of water or of hygroscopic materials. In such cases, generally materials of an oleaginous character are employed as the sole or main tempering agents for the colloid, the expression tempering agent being used herein to denote bodies which have the effect of so modifying the film of gelatinizing organic colloid as to enable the type faces of a typewriter, for instance, to break down or displace the ink-resisting medium without at the same time severing the fibres of the highly porous support for the ink-resisting medium of the stencil sheet.

Water-soluble soaps have been employed as the tempering agent when the gelatinizing organic colloid, such as gelatine or a like material, employed in the composition is dispersable in water.

Oils emulsified in the aqueous dispersion of the gelatinizing organic colloid by the use of suitable emulsifymg agents adapted to promote the formation of emulsions of the oil-in-water type have also been employed for the purpose in question.

It may be observed that water-insoluble salts of fatty acids have been used in the production of so-called wax stencils; such use is, however, not to be confused with the employment of these bodies in association with gelatinizing organic colloids.

The invention consists in a stencil sheet and a process of producing stencil sheets of the kind adapted to be stencilized without previous moisture in which the ink-resisting medium or coating of the sheet is substantially free from water or hygroscopic mate- 'rials or materials soluble in water and contains as its essential gelatinizing constituent a proteinin association with oleaginous materials in a proportion suflicient to maintain the composition permanently in a state in which it may be stencilized when substantiall-y free from water in association with a proportion of a water-insoluble soap.

As the majority of oleaginous materials exert a deleterious action upon rubber the choice of the oleaginous materials is in practice preferably restricted to such as will not harmfully affect the platen and feed rollers of typewriters and for this reason water 1nsoluble ricinoleic acid soaps are preferably used.

In accordance with the invention, when forming compositions containing water 1nsoluble soaps for use in the production of stencil sheets it is desirable to include in the composition a constituent which ensures that the composition will be a disperse system or emulsion of the oil-in-water type unt1l the setting or hardening has progressed to some extent and will then permit the formatlonof a disperse system or emulsion of the water-1noil type.

For example, in accordance with the 1I1Ve Il* tion, the composition may mltlally compnse a water insoluble soap and'a proportion of a volatile material adapted to restrain the tendency of the water insoluble soap to form a disperse system of the water-in-oil type while permlttmg, by its volatilization during setting or hardening, the water insoluble soap to exercise in a suitable degree its capacity to form a disperse system of the water-in-oil For instance, a volatile base such as ammon1a may be included in the composition for the purpose of ensuring the formation of a disperse system of the oil-in-water type and allowing, by its evaporation the water insoluble soap to exercise to a desired degree its capaclty to form a disperse system of the water-in-oil type.

- In this case, however, it is desirable or even" necessary that the proportion of ammonia relatlvely to the fatty acid should be considerably less than that which corresponds to one equivalent of ammonia to one equivalent of fatty acid and the proportion may with advantage be about one equivalent of ammonia to four equivalents of fatty acid.

The essential gelatinizing constituent of the mk-resisting medium may be a protein, such as gelatine, or carbohydrate colloid, such as agar, for example; preferably, the gelatimzlng constituent may comprise both gelatlne and casein.

As illustrative ofa suitable mode of producmg stencil sheets in accordance with the invention the following general description may be g1ven:

11 aqueous dispersion of gelatine is mixed with a proportion of ricinoleic acid in which zlnc oxide, or some other base yielding a water-insoluble ricinoleic acid salt, has been I previously dissolved. The resultant mixture will be a coarse emulsion of the water-ino1l type and to this emulsionis added a proportlon'of water containing ammonia in solution. By this addition the character of the emulsion is changed, the aqueous medium becoming the external phase; at the same time d the mixture becomes considerably thicker and 1n a suitable homogenized state and if necessary distended state by the addition of a further proportion of an aqueous medium it may be employed in coating Yoshino paper in the usual way. The coated sheets are allowed to dry and may be formolized. The stencil sheets produced, although they contain a considerable proportion of oily material, will not exhibit any pronounced tendency to sweat or exude oil.

The composition employed for coating the stencil sheets may be prepared by bringing together a paste consisting of 300 grams of ricinoleic acid and 300 grams of titanium white pigment, 700 grams of ricinoleic acid in which five grams of zinc oxide havev been dissolved with'the aid of heat, 500 c. c. of a 10% aqueous dispersion of gelatine and 400 c. c. of a 10% dlspersion of casein in halfnormal ammonium hydroxide solution, 500 c. c. of water being added to the mixture thus obtained and approximatel 750 c. cs. of normal ammonium hyd-roxi e solution being added.

Alternatively the composition employed may be free from casein in which case the proportion of the aqueous dispersion of gelatine therein will be increased to between 700 and 800 c. c.

In the above examples fatty acids other than ricinoleic acid might be employed but as stencil sheets are in the majority of cases stencilized in a typewriter, the employment of fatty acids other than ricinoleic acid 1s undesirable as in contradistinction to ricinoleic acid the other liquid fatty acids generally exercise a swelling action on rubber and thus will cause the rubber parts of the carrier of the typewriter with which the stencil sheet contacts to deteriorate.

It is to be pointed out that various changes may be made in the composition of the coating mass and theprocedure in the preparation of the same without exceeding the scope of the present application.

I claim:

1. Astencil sheet adapted to be stencilized by pressure comprising a sheet of Yoshino paper and a coating thereon, substantially free from water, adapted to be stencilized by pressure including a dispersion of a zinc salt of ricinoleic acid in coagulated gelatine and a proportion of an oleaginous tempering agent.

2. A process of producing stencil sheets which comprises'coating sheets-of Yoshino paper with an aqueous dispersion of a gelatinizing organic colloid, a water-insoluble soap an oleaginous material and a propor tion of a volatile material adapted to restrain the tendency of the water-insoluble soap to form a disperse system of the oil-in-water type, while permitting by its volatilization uring setting of the organic colloid, the water-insoluble soap to exercise its capacity to form a disperse system of the water-in-oil ,oil-in-water type, while permitting by its volatilization during setting of the organic colloid, the ricinoleic acid soap to exercise its capacity to form a disperse system of the water-in-oil type.

4 A process of producing stencil sheets which comprises coating sheets of Yoshino paper with an aqueous dispersion of a gelatlmzlng organic colloid, a water-insoluble soap an oleaginous material and a proportion of a volatile base adapted to restrain the tendency of the water-insoluble soap to form a disperse system of the oil-in-water type, while permitting, by its volatilization during setting of the organic colloid, the water-insoluble soap to exercise its capacity to form a disperse system of the water-in-oil type.

5. A stencil sheet adapted to be stencilized by pressure comprising a highly porous sup port with astencilizable coating thereon substantially free from water and water-soluble constituents and consisting essentially of a protein in association with an oleaginous material and a water-insoluble soap in a proportion adapted to maintain the composition in a state in which it maybe stencilized when substantially free from water.

6. A stencil sheet adapted to be stencilized in an air dry state comprising a base of open porous material coated with a substantially water free composition comprising a gelatinized organic colloid, a water-insoluble oily material and a water-insoluble soap as the sole tempering agents.

In testimony whereof I have signed my name to this specification.

ARMAND DE WAELE. 

